I am reading Semiconductor Physics and Devices (specifically pg. 78 of the pdf in link).
The formation of energy bands is discussed, and the following two sentences appears:
The wave functions of the two atom electrons overlap, which means that the two electrons will interact. This interaction or perturbation results in the discrete quantized energy level splitting into two discrete energy levels...
What I don't understand:
- What does it mean that the electrons interact? Does it mean that the potential of the electron is treated as a perturbation? Why is this the same as saying that their wavefunctions overlap?
- Is it really the perturbation caused by the presence of a second electron that causes the splitting of the energy (i.e. " the two electrons will interact"), or is it the perturbation due to a second proton? If there was just one electron and two protons would the energy spectrum not look the same? In the Kronig-Penney model only the periodic nuclei are taken into account; there is no reference to the other electrons in the system (at least none that I can find in the above book).